[Beowulf] Athlon64 / Opteron test

Joe Landman landman at scalableinformatics.com
Fri May 14 10:32:33 PDT 2004

Hi Joe:

  Quite surprised to see these numbers, as they don't seem to line up well with
what my customers are seeing.  Interesting data points though.  

  I see you are using an older (ancient) kernel for the e325.  I wonder if you
have all of your memory physically attached to one versus two processors.  Lots
of folks see slowdowns of some sort when they don't set up banking.

  I do know that some compilers (Intel specifically) check for processor
identity, and switch in or out the SSE2 versions of loops depending upon the
return code.  I also have heard cases where this (dramatically negatively)
impacts Opteron performance until it is "patched".  Greg Lindahl wrote about
this in a recent ClusterWorld article.

  Measurements we have done on non-engineering codes using the GCC, PGI, and
other compilers have shown that Xeons and Opterons are generally similar for 32
bit codes, to within a few percent.  When you recompile with the -m64 option
that you get some 5-30% advantages.  

  As you said, YMMV.  Its also quite easy to misconfigure these machines, and I
have seen this in a number of benchmarks.  The memory configuration can
(drastically) impact performance.  I might also suggest updating to a modern
kernel, one with at least some NUMA aware functionality.  2.4.18/2.4.19 was used
in the RedHat GinGin64 series.  This was not a good OS platform for benchmarking.

 Just some thoughts.


On Fri, 14 May 2004 08:25:12 -0700, Joe Griffin wrote
> Hi All,
> Originally this thread was about the choice of Athlon vs. Opteron.
> But the comparison between Opteron/Intel was brought up.
> I wish to state that the best choice is highly dependent
> on YOUR application.  I test various CFD and FEM
> engineering applications.  I have not only seen differences
> when comparing different application programs, but also
> when comparing different uses of the same program (say if a
> person changes a job from statics to dynamics).  The biggest question
> should be how YOUR application is used.
> Below is a web site comparing IA32, IA64 (linux and HPUX),  Opteron
> and an IBM P655 running AIX.   The site should only be used to
> compare hardare platforms when running our software.   I am sure
> that Fluent, LSTC/Dyna, Star-CD have similar sites.  I recomend
> finding out about the software that you will be using.
> MSC.Nastran Hardware comparison:
> http://www.mscsoftware.com/support/prod_support/nastran/performance/v04_sngl.cfm
> Regards,
> Joe Griffin
> Robert G. Brown wrote:
> >>In order to do the test, we have no doubt about the OS: Red Hat
> >>Enterprise 3, but we are a bit confused about the harware of choice:
> >>
> >>		Athlon64
> >>		Opteron
> >>
> >>As far as we know, Opteron has two main differences:
> >>
> >>	- A wider memory interface (128 bit in front of 64)
> >>	- A larger L2 cache memory (1 Mb)
> >>    
> >>
> >>3)
> >>
> >>Which is the most mature solution: AMD Opteron or Intel Itanium?
> >>    
> >>
> >
> >Did you mean mature or moribund;-)?  
> >
> >I'm only half kidding.  Itanium is dead as a doornail as technology goes
> >-- overpriced, underperforming, incompatible.  Intel is migrating to a
> >(more or less) Opteron compatible 64 bit processor as fast as they can
> >get there, as Major Software Companies (MSC) have announced that they
> >aren't going to do major ports to new chips with new machine languages
> >and compilers anymore if they can possibly avoid it.  If Intel dropped
> >the price of an Itanium to slightly LESS than that of an Opteron, I
> >think they'd still have trouble maintaining a market, because Opterons
> >are relatively easy to port to and will in principle run i386 code
> >(badly, of course) native.  Sometimes.  I haven't had a lot of luck with
> >it, of course, because you can't mix i386 code and 64 bit DLLs and we
> >installed a 64 bit version of the OS from the start, but theoretically
> >it will work.
> >
> >The good news is that Opterons are surprisingly fast for MY applications
> >for their relatively pokey CPU clocks, and some benchmarks show that
> >they can be really quite fast indeed for memory intensive applications
> >relative to e.g. an Athlon or P4 clock.  They also run much cooler than
> >regular Athlons (again for my application).  I draw ballpark of 185
> >watts loaded (dual CPU Opteron) vs 230 Watts or so loaded (dual CPU
> >Athlon) running more or less the same code.
> >
> >   rgb
> >
> >  
> >
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Joseph Landman, Ph.D
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://scalableinformatics.com
phone: +1 734 612 4615

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